Heat a charcoal or gas grill to medium high (about 375°F). Add the whole eggplants and allow the skin to char all over, turning every 5 minutes. After about 30 minutes, the eggplants will collapse. Remove to a colander and allow to cool.

Combine onion, 1 teaspoon of the kosher salt, and vinegar in a medium nonreactive bowl. Allow to marinate at least 5 minutes.

Once the eggplant is cool, scoop the flesh from the charred skin and coarsely chop it. Combine eggplant with marinated onions and remaining ingredients. Mix together gently and season well with additional salt and freshly ground black pepper to taste.